Underfeed stoker



July 12, '1938. E. B. BIRKENBEUEL UNDERFEED STOKER Filed Aug. 2'7, 1934 Patented July 12, 1938 I UNDERFEED' STOKER I Edward B. Birkenbeuel, Portland, reg., assignor to Iron Fireman Manufacturing Company,

Portland, Oreg.

Application August 21, 1934, Serial No. 741,582 r 3 Claims.

This invention relates generally to stokers, and particularly to underieed stokers.

The main object of this invention is thelconstruction of a coal burning stoker which will be inexpensive to construct and maintain, and which will not discharge gas or dust into the furnace room, regardless of operating or atmospheric conditions.

The second object is the provision of a novel form of draft arrangement and means for delaying the commencement of each air-supplying operation for a fixed interval of time after the commencement of a corresponding fuel-supplying operation. l These, and other objects, will become more apparent from the specification following as illustrated in the accompanying drawing, in which:

Fig. 1 is a perspective view of the device showing the wiring in diagram. Fig. 2 is a section taken along the line 2-2 in Fig. l in which the stoker is not being operated. Fig. 3 is a view similar to. Fig. 2 in which the stoker is being operated, and

Fig. 4. is a view similar to Fig. 3 showing the stoker operating but with the: air supply automatically reduced.

Similar numbers of reference refer to similar parts throughout the several views.

Before entering into-an explanation of this inventionitf will be understood that coal burning stokers have long been constructed in which a forced draft is supplied with the fuel which will, under certain conditions, produce a pressure within the combustion chamber in excess of that of the surrounding atmosphere, thereby causing gas and ashes to be blown from the furnace into the furnace room. A further diiilculty which is.

always present with this type of underfeed stokers resides in the smoking or gassing through the coal hopper, due to the positive pressures existing within the plenum chamber, which-diiilculty is laid to the use of auxiliary air lines, closed hoppers, and other expedients forthe purpose of preventing gassing. In the invention which I am about to describe 'a negative pressure is maintained within the combustion chamber by the use of an exhaust fan in the smoke pipe of the furnace, thereby poslbut that the application of an exhaust fan to the smoke pipe of a furnace to which fuel is supplied by an underf eed stoker is entirely new.

Referring in detail to the drawing, there is shown a common form of warm air furnace l0 into the combustion chamber of which projects the retort ll of an underfeed stoker to which coal is -fed through the tube l2 from a hopper i3 by means of a fuel feed worm it which is driven through suitable gearing in the transmission It by means of a motor iii. The motor I6 is con- 10 trolled by means of a thermostat ll, or other form of switch placed in the circuit it.

Surrounding the retort ii is an air box It having an inlet opening 28 provided with double closures 2| and 22, both of which are hinged on 15 the pivot 23. The closures 2i and 22 are adjustably held in an. angular relationship by means of the quadrant 24 and the clamp screw 25.

To the closure 2i is attached the rotatable screw .26 which may be operated by means of the 20 head 21 on the outer sideof the closure 2i. The collar 28 is secured on the screw 26 on the inside of the closure 2| for the purpose of holding the screw 26 against endwise movement with relation to the closure 2i. 25

Supported on the screw 28 is the under slung weight 29 through the upper end of which the screw 26 is threaded. The purpose of this construction is to permit the weight 29 to be adjusted with relation to the closure 2i. 3-)

The smoke outlet 38 of the furnace III is connected to the centrifugal fan 3i whose discharge pipe .32 connects with the stack 33 provided with the usual clean-out 3t.

The fan 3i is provided with a pulley 35 which 35 is driven by the belt 36 from the pulley 31 to the fan motor 38. The lead wires 39 of the motor 38 are connected to the time delay relay Ml which is energized through the wires II from the circult It.

Any suitable time delay relay 40 may be employed which will delay the commencement of the operation of the motor 38 after the commencement of the operation of the motor It.

- which will feed coal upwardly into the retort ll. After a fixed interval of time, due to the operation of the time interval relay III, the motor 38 will be energized and the fan 3| will cause the 55 products of-combustion to be drawn from the furnace l0 and discharged into the stack 33.

If there are any leaks around the fire door 42, or the secondary air openings are not closed, then air is positively drawn in through these leaks or openings, thereby insuring against a reverse condition if there should be a sudden changein the atmospheric conditions which would affect the natural stack pull.

It will be noted that until the fan 3| commences to operate, the closure 2i is in the position shown in Fig. 2 but the operation of the fan ill will cause the closure 2| to move to the position shown in Fig. 3 in which the required amount of air is admitted to the combustion chamber. If, however, for any reason, such as a speeding up of the fan or a low coal level in the retort, the velocity of air passing through the opening 20 increases, then the closure 22 will move toward a closing position (as shown in Fig. 4) making the device self-regulating, while the closure 2| provides automatic banking when the stoker is shut down.

It can be seen from the foregoing that by this simple arrangement it is possible to burn coal without permitting any dust or gas to escape from the furnace into the furnace room.

I claim:

1. The combination with an underfeed stoker including thermostatically controlled coal feeding means and a retort, of a furnace, an exhaust fan in the smoke pipe of said furnace, and means for delaying the commencement of each fan operation until after the commencement of each fuel feeding operation.

2. The combination of claim 1, together with an air duct leading to the retort, and a double damper for limiting the flow of air thru said duct while the fan is operating and for preventing the flow of air therethrough when said exhaust fan is not operating.

3. In combination, a furnace, a retort for heating said furnace, motor driven means for feeding coal to the retort, an air duct leading to said retort and having an inlet opening, a damper having two connected closures mounted so that each of the closures may move to a position to close said inlet opening, a blower having its suction side connected to the furnace smoke pipe, an electric circuit, including a room thermostat, for operating the motor and the blower, and means for delayingthe operation of the blower until after the coal feeding means has operated thru a time interval.

' EDWARD B. BIRKENBEUEL. 

